Transformer



April 11, 1950 H. HARTMANN TRANSFORMER Filed Dec. 3, 1946 of iron,

Patented Apr. 11,

TRANSFORMER Hans Hartmann, Baden, Switterland, assignor to Aktiengesellschaft Brown, Boverl 8; Ole, Baden.

Switzerland, a .ioint-stoc Application December 3,

k company 1946, Serial No.

In Switzerland December 21, 1945 1 Claim. (01. 175-358) In the construction of current transformers of the instrument type, the use of one-piece annular core laminations is preferred for the reason that it assures a high order of measuring accuracy and also permits the use of a special high permeability iron that is supplied practically exclusively in annular form. However since the annular core laminations form unbroken rings the use of prewound coils is obviously precluded and both the primary and secondary windings of the transformer must hence be wound on the core.

One of the problems encountered with this mode of construction is the provision of adequate insulation between the transformer windings and it is the principal object of this invention to provide an improved arrangement for obtaining ood insulation between these windings. According to the invention, the primary and secondary windings which form interlinked rings crossing one another at right angles are insulated from each other by an insulating sleeve of paper laminations applied to one of the windings at the crossing place, the several layers of insulation being slit lengthwise from the opposite ends to provide tabs which are bent outwardly to form flanges.

In the accompanying drawings in which Fig. l is a longitudinal view in section that illustrates a constructional example of the invention, Fig. 2 a section taken on lines 2-2 of Fig. 1, and Fig. 3 a plan view of the strip material used for insulating the windings, the transformer is seen to comprise an annular iron core I made up from a stack of annular laminations and on it is wound the secondary winding 2 of the current transformer. Preferably a two-part shell 3 surrounds and encloses the core and secondary winding and on this shell is wound a plurality of layers of paper strip insulation 4. The shell 3 is not absolutely necesary but .its use does assure a better fleld distribution. The lead-off conductors 2a and 2b of the transformer secondary winding 2 can be insulated in known manner and are taken out through shell 3 and insulation 4 at the side opposite the primary winding 5 of the transformer. The latter with lead-oil conductors in and 5b is likewise of annular shape and it is wound upon the core Icarrying the transformer secondary 2 so that the two annular transformer windings cross each other. At the crossing place, insulation 6 of laminated paper is applied on the insulation 4 and thereby surrounds a segment of the core and secondary winding. As shown in Fig. 3, the paper strip material used for forming the multi-layer insulation 6 is slit inwardly from its two sides to the edge of the primary winding to form narrow tabs 6a so that as it is wound upon the insulation I the tab portions are substantially free to closely follow its arcuate contour. After the primary winding 5 is completed, the tab portions formed at the ends of the several layers of insulation 6 are turned back so that they form end flanges 6b and 60 between which lies the primary winding 5. The flange portions 6b, 60 have a, natural spreading characteristic which can be increased by the insertion of split rings 1 to thereby further improve the insulation betwen the primary winding and the core.

As an alternative arrangement, the insulation winding 6 between the annular interlinked primary and secondary windings instead of being provided only On the insulation 4 could likewise be also applied at the same time on the primary winding. To increase the strength of the insulation between the primary winding and the core, and between this winding and the transformer casing (not shown), a rim of insulation 8 consisting of a plurality of layers of paper is applied to the outer periphery of the primary winding 5. In forming the insulation 8, the paper sheeting used for winding it may also be slit in from the side edges to form narrow tabs 8a that are then turned inwardly so as to lie flatly against the sides of the primary winding.

Although the core and secondary winding have been illustrated as being completely enclosed by the insulation 4, this is not necessary and the insulation may be applied only where the two annular windings ing a considerable I claim:

A current transformer comprising an annular iron core of uninterrupted annular laminations, an annular secondary winding on said core, an annular primary winding interlinking said core and secondary winding, and means insulating said annular windings from each other comprising a multi-layer insulating sleeve of sheet material having slits extending inwardly from its two side edges to form a plurality of tab portions. said insulation sleeve surrounding one of said transformer windings where it crosses the other transformer winding and the tab portions thereof extending outwardly to form flanges which lie against the opposite sides of and support said other winding.

amount of material and labor.

HANS HAR'IMANN.

(References on following M) cross each other thereby sav- REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Rupley Feb. 28, 1905' Biermanns Oct. 12, 1926 Schrader Aug. 23, 1932 Kelnath et a1 Nov. 29,- 1932 Verrill Dec. 23, 1941 Number 10 Number Name Date Meyerans June 30, 1942 Camilli Apr. 13, 1943 Camilli Oct 5, 1943 Camilli July 25, 1944 Meyerans Oct. 22, 1946 Camilli Nov. 2, 1948 FOREIGN PATENTS Country Date Great Britain June 30, 1932 

